Push-to-talk (PTT) systems are generally half-duplex communications systems, where mobile terminals are able to communicate with each other, typically through a base station. In many cases, a network of interconnected base stations is used to connect mobile terminals across a large geographical area.
Many PTT systems enable group communication, wherein a single message or voice transmission can be transmitted to a group of users. PTT is thus popular with emergency services, as it provides an efficient means of communication to a large number of users.
It is often desirable for a device to monitor multiple talkgroups simultaneously, particularly in the case of emergency services. In particular, while different talkgroups may be allocated to fire, medical and law enforcement personnel, it is often desirable for these groups to be able to receive each others' communications. In such case, PTT talkgroups are typically monitored by scanning the talkgroups listed in a scan list, wherein priorities are allocated to talkgroups in a scan list to ensure that media from a higher priority talkgroup is played.
In the case of Land Mobile Radio (LMR) based PTT, each radio can monitor a control channel to obtain a talkgroup call status. In the case of cellular broadband based PTT, such as PTT over 3rd Generation Partnership (3GPP) Long Term Evolution (LTE), for example, a talkgroup call can utilize a broadcast service, a unicast service or a combination thereof, depending on where individual user communication entities are located and other factors. A 3GPP LTE device can learn about broadcast talkgroup call status in an evolved Multimedia Broadcast Multicast Service (eMBMS) area through broadcast or unicast control signaling, and where unicast resources are used, through unicast control signaling.
However, a problem with cellular broadband based PTT systems of the prior art is that unicast control messages and media are generally inefficient. In particular, LTE devices generally must transition to a “connected” mode to receive the control messages or media, which reduces battery life. Furthermore, control messages and media generally utilize a relatively large amount of network resources.
Accordingly, there is a need for an improved group communication system and method.
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The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.